Noise-Induced Magnetic Field Saturation in Kinetic Simulations

Abstract

Monte Carlo methods are often employed to numerically integrate kinetic equations, such as the particle-in-cell method for the plasma kinetic equation, but these methods suffer from the introduction of counting noise to the solution. We report on a cautionary tale of counting noise modifying the nonlinear saturation of kinetic instabilities driven by unstable beams of plasma. We find a saturated magnetic field in under-resolved particle-in-cell simulations due to the sampling error in the current density. The noise-induced magnetic field is anomalous, as the magnetic field damps away in continuum kinetic and increased particle count particle-in-cell simulations. This modification of the saturated state has implications for a broad array of astrophysical phenomena beyond the simple plasma system considered here, and it stresses the care that must be taken when using particle methods for kinetic equations.

15 pages, 4 figures

References in corpus (5)

• One-to-one direct modeling of experiments and astrophysical scenarios: pushing the envelope on kinetic plasma simulations
• Exploring the Statistics of Magnetic Reconnection X-points in Kinetic Particle-in-Cell (PIC) Turbulence
• Dynamo in weakly collisional nonmagnetized plasmas impeded by Landau damping of magnetic fields
• Low Mach-number collisionless electrostatic shocks and associated ion acceleration
• Temperature-dependent Saturation of Weibel-type Instabilities in Counter-streaming Plasmas

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• An Energy Conserving Vlasov Solver That Tolerates Coarse Velocity Space Resolutions: Simulation of MMS Reconnection Events
• An investigation of shock formation versus shock mitigation of colliding plasma jets
• Discontinuous Galerkin Representation of the Maxwell-Jüttner Distribution
• Attosecond dispersion as a diagnostics tool for solid-density laser-generated plasmas